Concept
STT on Expiry: Why the Charge Can Be Larger Than Expected
When an option is sold in the market, STT applies to the premium. When an in-the-money option is instead allowed to expire and is exercised, the charge is computed on the settlement value of the contract rather than on the premium — a very different base.
How to read it
- A normal exit is a sale, and the tax base is the premium received.
- An exercised contract is not a premium transaction. The base becomes the settlement value, which reflects the full contract rather than the option’s price.
- Because premium and contract value can differ by orders of magnitude, the same position can attract very different charges depending on how it ends.
Why the base matters so much
Consider an index option held to expiry that finishes slightly in the money, with a premium of around ₹15 and a contract value in the region of ₹14 lakh. Charging a percentage of ₹15 per unit and charging a percentage of the settlement value are not remotely the same calculation, even at similar-looking rates. Traders regularly report contract notes where the tax on an expired in-the-money option exceeded the profit on the position. Nothing irregular occurred — the base simply changed when the contract was exercised rather than sold. Understanding this before expiry is the point; what you choose to do about it is your decision.
What it does not tell you
- Rates and bases are set by law and revised in budgets, so any specific figure dates quickly. Confirm the current rate with your broker or the relevant circular rather than relying on a summary.
- CernoQuant’s own charge calculator models premium-based STT and explicitly does not model exercise-based STT, because that requires the settlement price. The calculator flags this rather than reporting a number it cannot compute.
- Broker contract notes are the authoritative record of what was actually charged.
Frequently asked questions
Why was STT so high on my expired option?
Because an exercised in-the-money option is charged on the contract’s settlement value rather than on the premium. Those two bases can differ enormously, so the same position produces very different charges depending on whether it was sold or exercised.
Does this apply to out-of-the-money options?
No. Options expiring out of the money are not exercised and no settlement-value charge arises.
What is the current STT rate?
Rates are set in legislation and revised periodically, so quoting a figure here would date. Check the current rate with your broker or the relevant circular, and treat your contract note as authoritative.
Does CernoQuant calculate this automatically?
The charge engine computes premium-based STT accurately. For exercised in-the-money options it flags that the exercise basis requires the settlement price rather than reporting a figure it cannot verify.
Related
- Expiry Day Mechanics — Concept
- Physical vs Cash Settlement — Concept
- Slippage — Concept
Educational use only
This page is educational material about how a technical tool is calculated and read. It is not investment advice, not a recommendation to buy or sell anything, and not a signal service. No indicator predicts future prices. CernoQuant is a trading journal and analytics platform, not a SEBI-registered investment adviser. Trading decisions and their outcomes are yours alone.
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